1. Field of the Invention
The present invention generally relates to a position signal processing apparatus, and more particularly to a signal processor of a motor absolute position signal processing apparatus.
2. Description of Prior Art
Servomechanism system refers to a system for controlling the position, speed or acceleration of a mechanical system by a close loop control method. In general, a servo system usually includes several main parts including a plant, an actuator, and a controller, and the plant is a controlled object such as a mechanical arm or a mechanical working platform. The main function of the actuator is to provide power to the plant by pneumatic, hydraulic, or electric driving method. If the hydraulic method is adopted, the actuator is generally called a hydraulic servo system. At present, a vast majority of servo systems adopt the electric driving method, and the actuator includes a motor and a power amplifier, and a special design applied to a motor of the servo system is called a servo motor, which usually includes a position feedback device such as an optical encoder or a resolver. The servo motors mainly used in the industry include DC servo motors, permanent magnet AC servo motors and induction AC servo motors, and the permanent magnet servo motors are used most extensively. The function of the controller is to provide a close circuit control such as torque control, speed control and position control for the whole servo system. In general, the present industrial servo drives usually include a controller and a power amplifier.
The aforementioned servo motors generally include a position feedback device, and the optical encoder provides an incremental signal and an absolute position signal, and the incremental signal and absolute position signal output two sets of differential signals respectively “SIN;/SIN (inverted signal)” and “COS;/COS (inverted signal)”. The absolute position signal mainly provides a start position signal of the optical encoder to the motor absolute position signal processing apparatus for the processing, and the processed signal is transmitted to the signal processor for the determination. If the optical encoder starts operating together with the installed electric machine, the signal processor (DSP or MCU) switches processing the incremental signal. Since the absolute position signal just uses the optical encoder for the positioning stage before starting the operation, therefore the motor absolute position signal processing apparatus requires a separator circuit detection with two sets of signal integration amplifiers and two sets of optical couplers (as shown in FIG. 1) to process two sets of differential signals respectively: SIN;/SIN (inverted signal)” and “COS;/COS (inverted signal)” of the absolute position signals. Obviously, the level of complexity of the circuit design becomes higher. In addition, the power supplied to the optical encoder is separated from the signal processor DSP (or MCU). At present, an analog signal device with a transmission separation function usually comes with a large size and a high price, and thus the cost will be very high if the design of two sets of detection circuits is adopted.